In the realm of optoelectronics, packaging has become a crucial factor in the ability to manufacture reliable optoelectronic devices and systems. Passive alignment of a device and the subsequent packaging of the device is critical in assuring the ability to mass produce devices and systems as well as to manufacture systems and devices as at as low cost as is possible. Of course, the packaging and passive alignment of devices and systems requires a great deal of precision in order to meet the required performance characteristic. To this end, while active alignment and packaging of devices offers precision in the alignment of the device and subsequent packaging, the attendant costs in packaging, as well as the inability to produce a large quantity of devices and systems has lead to the need for a package which is precisely aligned in a passive manner.
One area of technology which holds great promise in the realm of packaging optoelectronic devices and the passive alignment of both active and passive devices in an optoelectronic system is silicon waferboard technology. In silicon waferboard technology, monocrystalline materials are used to effect the passively alignment with great precision. The use of silicon waferboard enables precision passive alignment through the use of well known and precisely defined monocrystalline planes of a monocrystalline material, to effect the passive alignment of the devices in the system. One example of a subassembly for an optoelectronic device is as found in U.S. Pat. No. 4,897,711 to Blonder et al, the disclosure of which is specifically incorporated herein by reference. The reference to Blonder et al has a silicon bench on which there is formed a v-groove for the placement of an optical fiber and a selectively disposed reflective surface etched in the silicon for alignment of the optical beam to and from a fiber to a detector or from a transmitter depending on the application. This silicon bench alignment structure enables the passive alignment of the device to the fiber. Thereafter the silicon bench is disposed on a dual in line package having a lead frame mounted thereon. Finally, a cover member is disposed to encase the packaged assembly.
As can be appreciated from a study of the above reference to Blonder, et al, there is a great deal of complexity in the fabrication of the design. While the reference to Blonder does disclose some advantages in packaging gained through the passive alignment of the optical fiber to the device, there are disadvantages to such a structure as well. These disadvantages are primarily manifest in a complexity in assembly, as well as in the potential mismatch of differing materials of the subassembly which can impact greatly the performance of the device. First of all, the silicon waferboard subassembly of the invention to Blonder et al rest on a metal lead frame which is further disposed in the dual in line package as is shown in FIG. 1 of the above-referenced patent. The various parts of this assembly as disclosed in the Blonder et al reference to include the dual in line package header, lead frame and cover are generally of differing material compositions. Accordingly, each material will have different thermal expansion and contraction properties. In such a system, there is a relatively large distance between the entrance of the optical fiber to the package and the point of interaction between the fiber endface and the device. When the device heats and cools, the various members will expand and contract in differing degrees resulting in strains and stresses on the optical fiber and thereby potential misalignment of the fiber to the device. Furthermore, the assembly of such a package has attendant complexities which will increase the overall complexity of the fabrication of the packaged assembly. The optical fiber is fixed in two locations, first at the substrate preferably silicon waferboard, and at the package wall. It is therefore required to put a slight bend in the fiber to isolate the stress in the fiber from the package wall. This results in complex assembly of the final product. Additionally, alignment is done only once the package is committed to the assembly. If the alignment is poor, the package is lost along with the component, resulting in increased cost of fabrication and a reduced yield. Finally, the assembly as disclosed in the reference to Blonder et al, is a pigtailed assembly. What is required is an assembly readily amendable being disposed in connector form while utilizing the attendant advantages of passive alignment as described supra and infra.
Accordingly, what is desired is a less complex assembly for mounting the optical subassembly on a single material and in a smaller package thereby reducing the costs of not only the material, but also the complexity of the fabrication and thereby the cost of the assembly, while maximizing operating performance. There is also the need to retain the required performance through passive alignment techniques. What is needed is a package for an optoelectronic device disposed on a silicon optical bench which is thereafter mounted on a mounting structure of a single material, thereby reducing potential misalignment due to thermal mismatch of materials. Furthermore, what is needed is a shortened distance from the point of entry into the package to the point of mounting on the silicon optical bench thereby reducing the stress on the fiber due to potential thermal mismatch that can occur between various elements of the package due to the thermal mismatch of the various materials.